A known device disclosed, for instance, in JP-A-2003-14683 detects an abnormality caused by a broken element of an oxygen sensor (hereinafter also referred to as a “sensor”) installed in the exhaust path of an internal combustion engine. The oxygen sensor includes a sensor element, which is positioned between the atmosphere and exhaust gas, and outputs a voltage according to the oxygen partial pressure difference between the exhaust gas and the air in the atmospheric layer. When the resulting voltage output pattern indicates that the oxygen partial pressure difference is small or reversed, the device concludes that the sensor element is defective and then makes an abnormality diagnosis.
Patent Document 1:
Japanese Patent Laid-Open No. 2003-14683
Patent Document 2:
Japanese Patent Laid-Open No. 2004-353494
Patent Document 3:
Japanese Patent No. 3562030